Organic light-emitting diode (OLED) devices are active light-emitting devices. Compared with the thin film transistor LCDs (TFT-LCDs) in the existing mainstream flat panel display technology, OLEDs, due to their advantages such as high contrast, wide angle of view, low power consumption, smaller size and the like, are expected to become the next-generation flat panel display technology following LCDs, and are one of the technologies that are highly concerned among the existing flat panel display technologies.
An OLED device generally comprises an anode, an hole transport layer (HTL), an emission layer (EL), an electron transport layer (ETL), and a cathode. In the prior art, the electron transport layer is typically made of a single organic material. However, an OLED device prepared by using the electron transport layer made from the single organic material typically has a relatively high driving voltage and a relatively low efficiency, leading to problems of high power consumption of an OLED screen, short service life and the like. In an organic electroluminescent device, in order to lower the operating voltage of the device and improve the charge balance between electrons and holes, it is necessary to improve the electron injection and transport efficiency. In the existing technologies for improving the electron injection efficiency, it is necessary to define the material of a cathode following the electron transport layer, and this cathode material is required to have one metal which may reduce metal ions in an organic complex to a corresponding metal in vacuum. This restricts the selection of the cathode material.